This invention relates generally to gypsum board, and more specifically to a method and apparatus for fabricating gypsum board.
Conventional gypsum wallboard or drywall is typically manufactured from a gypsum plaster slurry which is put between two layers of paper. More specifically, in the conventional method, a wet slurry of gypsum is poured on a conveyor between two layers of paper, and the slurry is allowed a certain amount of time to set. In gypsum wallboard, the two layers of paper contain the slurry and provide the tensile strength required in installation and use.
In at least some known fabrication methods, the conveyor is a closed loop conveyor that can travel at speeds of four hundred feet per minute or faster. The conveyor enables the wallboard to be fabricated using rolls of paper and accordingly, includes at least a longitudinal edge forming system, a cutting system, and a drying system. The edge forming system uses wedge shaped raised edges along the conveyor that create recessed areas along the longitudinal edges in the face of the wallboard prior to the wallboard being fully cured. When the wallboard is later cut to size and installed, the recesses are filled with drywall compound, taped over, and finished to produce a smooth joint.
The cutting system enables the wallboard to be cut into predetermined discrete lengths such that substantially rectangular wallboard members are formed. The cutting system is adjustable to allow different lengths of wallboard to be cut without substantial interruption of the manufacturing operation.
After being cut, the wallboard members are moved away from the cutting station to a loading area where they are loaded into a drying system to dry the cut wallboard members.
Known wallboard includes recessed areas that extend along both of the opposed longitudinal edges of the wallboard. The recessed areas are formed by the raised edges on the conveyor. The recessed areas are in the shape of inclined planes that taper from the face of the wallboard to the longitudinal edges and have a maximum depth at the side edges of about 0.05″ below the face of the wallboard.
When the wallboard is cut by the cutting system, panels of conventional wallboard are formed which are bordered by the opposed recessed longitudinal edges and by a pair of lateral non-recessed edges that connect the longitudinal edges. More specifically, the wallboard is typically cut such that the panels are fabricated with a longitudinal length that is commonly eight feet, ten feet, twelve feet, fourteen feet, or sixteen feet. For maximum efficiency and conservation of plant space, the same line must have the capability of fabricating all of the different lengths of wallboard without a major shutdown of the line.
During installation, depending on the length of the wall being formed by the wallboard, wallboard panels are typically positioned for installation such that the longitudinal edges are parallel to the floor, an installation known as a “horizontal orientation”. In this installation, a longitudinal recess of a first panel is adjacent to a longitudinal recess of the adjacent panel. This forms a longitudinal recessed joint. A drywall compound fill material and tape are then used to seal the recessed joint formed by the recessed longitudinal edges of the panels. Specifically, the recessed areas of the joints are filled with the drywall compound, taped and smoothed across the joint, such that the joint is covered without the compound creating an unsightly bulge extending outwardly between the panels. Installing the wallboard panels such that the longitudinal length extends horizontally along a wall parallel to the floor, rather than vertically and substantially perpendicularly to the floor, facilitates faster installation time of the wallboard panels, and faster finishing time of the installed wallboard panels. In addition, when wallboards are installed in a vertical orientation, installation and labor costs may be increased as the installers and tapers must use ladders for installation and finishing.
When wallboard panels are installed on longer walls and ceilings, because the recessed areas only extend along two longitudinal edges of each panel, a butt joint may be formed between the lateral edges of two adjacent panels. Such joints must still be covered with tape and compound, but because the lateral edges do not include a recessed area, the joint compound must be spread over a wider area than those of the longitudinal joints to facilitate blending the butt joints into the wall surface without creating unsightly bulges.